Color filter comprising unit patterns with varied densities and liquid crystal display device using the color filter, and their manufacturing methods

ABSTRACT

An object of the invention is to provide a color filter and a liquid crystal display device using the filter, which can obtain well-balanced color purities within a pixel. A color filter for coloring a first light ray L 1  having a unidirectional optical path and a second light ray L 2  having a bidirectional optical path for each pixel. The color filter includes a first area portion  10   t  in which the first light ray L 1  is caused to be transmitted and a second area portion  10   r  in which the second light ray L 2  is caused to be transmitted, for each pixel. The first area portion  10   t  and the second area portion  10   r  respectively have structures by which different coloring effects are exerted if light rays having the same optical path and the same property pass through them.

BACKGROUND OF THE INVETNION

1. Field of the Invention

The present invention relates to a color filter and a liquid crystaldisplay device using the color filter.

In particular, the present invention relates to a color filter whichhandles a first light ray and a second light ray. The first light rayhas such a uni-directional optical path that the light ray incident fromone principal plane side of the filter passes through the filter onlyonce to be colored and is guided to the other principal plane side ofthe filter. The second light ray has such a bi-directional optical paththat the light ray incident from the other principal plane side of thecolor filter passes through the filter to be colored and the passedlight ray is reflected by an optical reflective element or the likedisposed in the one principal plane side to enter the filter again andpass to be colored, and comes back to the other principle plane side.The invention also relates to a method of manufacturing the colorfilter. The invention further relates to a liquid crystal display deviceusing such a color filter, and to a method of manufacturing the liquidcrystal display device.

2. Description of Related Art

A liquid crystal display device, what is called the transflective typeliquid crystal display device, becomes in full practical use, whereinexternal light incident from the front side is reflected to be guided tothe front side while being provided with an optical modulation accordingto the image to be displayed, and incident light from the back lightsystem on the rear side is passed to the same front side while beinglikewise provided with the optical modulation according to the image tobe displayed. This type of liquid crystal display device effectivelyperforms displays of image based on the external light (ambient light)mainly when the operating environment is bright (reflective mode) andbased on emission light from the back light system mainly when it isdark (transmissive mode).

Such a type of liquid crystal display device is disclosed in a prior artdocument, “Development of Advanced TFT with Good Legibility under AnyIntensity of Ambient Light” by M. Kubo et al., IDW' 99, Proceedings ofThe Sixth International Display Workshops, AMD3–4, page 183–186, Dec. 1,1999, sponsored by ITE and SID. In this device, each pixel electrode isdivided into a reflection area and a transmission area. The reflectionarea is a reflection electrode part formed from aluminium with which anacrylic resin with a rough surface is covered, and the transmission areais a transparent electrode part formed from ITO (Indium Tin Oxide) witha flat surface. The transmission area is situated in the center of arectangular pixel area and has a substantially similar rectangularfigure like the pixel area, whereas the reflection area is a part of thepixel area other than the rectangular transmission area and has a formof surrounding the transmission area. By virtue of the pixelconfiguration etc, the legibility is improved.

SUMMARY OF THE INVENTION

However, in the prior art liquid crystal display device, thetransmission area and the reflection area are different in color purityof the displayed color although these areas are in the same pixel area.It is supposed that this problem results from the color filter in theprior art in which the light from the back-light system and the externallight whose optical paths are different from each other are colored inmuch the same fashion. As a result, the quality of the displayed colorsis deteriorated over the display area.

In view of the above-mentioned points, it is an object of the presentinvention to provide a color filter and a liquid crystal display deviceusing the color filter, which can show the well-balanced color puritieswithin a pixel.

It is another object of the present invention to provide a color filterand a liquid crystal display device using the color filter, which cansatisfactorily reproduce chromaticity over a display area.

It is a further object of the present invention to provide methods ofmanufacturing the color filter and the liquid crystal display device.

In order to achieve the object mentioned above, one aspect of a colorfilter according to the present invention is a color filter for coloringa first light ray having a unidirectional optical path and a secondlight ray having a bidirectional optical path for each pixel, the colorfilter including a first area portion in which the first light ray iscaused to be transmitted and a second area portion in which the secondlight ray is caused to be transmitted, for each pixel, the first areaportion and the second area portion respectively having structures bywhich different coloring effects are exerted if light rays having thesame optical path and the same property pass through them.

According to this aspect, by virtue of the constitution, it is possibleto desirably set the balance of a coloring effect for the first lightray in the first area portion in the transmission mode and a coloringeffect for the second light ray in the second area portion in thereflection mode, so that well-balanced color purities can be acquiredwithin a pixel.

In this aspect, the first area portion and the second area portion mayhave such a difference in structure that a coloring effect performed forthe first light ray within a pixel by the first area portion issubstantially equal to a coloring effect performed for the second lightray within a pixel by the second area portion under predeterminedconditions. This scheme enables the coloring effects to be substantiallyequal, and much the same good visibility to be always ensured in thereflection mode as well as in the transmission mode.

Also in this aspect, the first area portion and the second area portionmay have such structures that their densities of coloring elements aredifferent from each other, or the second area portion may comprise acoloring portion that colors the second light ray and at least onecolorless portion that transmits the second light ray substantially withcolorlessness. According to this solution, it is possible to easy make adifference of coloring effect between the first area potion and thesecond area portion.

Furthermore, in this aspect, each of the first area portion and thesecond area portion may be formed based on a plurality of coloringelement construction units, and the coloring element construction unitsof the first area portion may have a higher density than those of thesecond area portion. In this way, densities of coloring elements formedof the first and second area portions are changed in dependence on theplurality of coloring element construction units, so that the desirablecoloring effects can be easy obtained by means of a normal patterningprocess or the like. Alternatively, each of the first area portion andthe second area portion may have a coloring element surface that ispatterned based on a plurality of unit patterns, and the first areaportion and the second area portion may have different densities of theunit patterns. This offers an advantage in that a difference of aneffective surface area size or volume of the coloring elements betweenthe first area potion and the second area portion can be easy obtainedby the patterning process. For example, there may be a color filtercharacterized in that the unit pattern is projection-shaped, and theunit patterns of the first area portion has a higher density than theunit patterns of the second area portion and be a color filtercharacterized in that the unit pattern is depression-shaped, and theunit patterns of the first area portion has a lower density than theunit patterns of the second area portion. In the latter waysrespectively, the color filter according to the present invention can beobtained with ease and reliability.

Alternatively, the first area portion and the second area portion mayhave coloring element surfaces that are patterned based on a pluralityof first unit patterns and on a plurality of second unit patterns,respectively, and the unit pattern densities of the first area portionand the second area portion may be determined in such a manner that thefirst and second area portions have such structures that coloringelement forming densities of the first and second area portions aredifferent from each other. This way means to propose examples in whichdifferent kinds of unit patterns are provided and configured for theunit pattern. Likewise, the first and second area portions exerting thedesirable coloring effects can be easy obtained. Thereupon, the firstunit pattern may have one of projection shape and depression shape, andthe second unit pattern may have the other of projection shape anddepression shape, so that the first and second area portions can beobtained with ease and reliability.

In the case of using the unit pattern, it preferably has a shape with afunction of diffusing incident light. Accordingly, the diffused lightallows a viewing angle characteristic to be improved over a displayscreen, and contributes to improvement of visibility.

In the above-mentioned aspect and the other kinds of concrete modesthereof, the first and second area portions can be formed with the samecoloring material. This feature is characterized in that the structures(instead of the properties) of the coloring materials of the first andsecond area portions are altered to make their coloring effectsdifferent even in using the same coloring material. Thus characterizedfeature allows to avoid both processes of a forming process for thecoloring material for the first area portion and a forming process forthe coloring material for the second area portion. In other words,because of changing the structures of the formed coloring elements ofthe same material for getting the different coloring effects, it is notnecessary to form the first and second area portions with the individualmaterials. Accordingly, the area portions require only one processwherein both are (simultaneously) formed with the same material, wherebysimplification of manufacture is achieved.

In the above-recited aspects and modes thereof, the color filter mayfurther comprise a protective film covering the first and second areaportions, preferably. This scheme enables to flatten the surface of thefirst and second area portions that have different structures, and tostrengthen the construction of the color filter.

In a certain mode of having at least one colorless portion in the secondarea portion, a plurality of the colorless portions are dispersedlylocated over the second area portion. According to this mode, thecolorless portion makes the second light ray pass therethrough withoutcolor, so that its coloring efficacy on the second light ray can bereduced. This leads to retainment of the well balanced color purities ofthe first and second light rays obtained, so as to improve the qualityof the displayed colors over the whole display area.

Also in the certain mode, the pixel area may have substantially apolygon shape on the plan view, and the colorless portion may be locatedin the vicinity of a corner of the polygon in a pixel area. By thuslocating the colorless portion in the corner side of a pixel area, itbecomes an advantage that the colorless portion is easy to be formedmore accurately in comparison with the case of locating it at the innerposition of a pixel area (i.e. close to the center of a pixel area).

Alternatively, the pixel area may have substantially a polygon shape onthe plan view, and the colorless portion may have a shape ofsubstantially a triangle including a corner of the polygon and having anoblique side opposed to that corner in a pixel area. Such a triangularcolorless portion contributes to minimization of the length of anoutline adjacent to the coloring portion, so that the step portionbetween the coloring portion and the colorless portion is smaller tothereby suppress the undesired behavior of light possibly caused in thestep portion. In addition, the colorless portion may beisosceles-triangle-shaped on the plan view. In this case, it is able toevenly limit the variation of the effective area size of the colorlessportion, which is caused by the displacement of the mask for patterningthe coloring portion.

Furthermore, in the certain mode, shielding means may be preferablyprovided to a boundary of the pixel area. This preferred example offersan advantage in that the effective area of colorlessness of thecolorless portion can be easy and accurately designed to the desiredvalue. In particular, if the colorless portion is thus triangle-shaped,then all corner portions of the colorless portion are hidden by theshielding means such as the black matrix and all outline portions of thecolorless portion appearing within a pixel area become linear shapes, sothat the resultant variation of the effective coloring area can be madeextremely smaller. That is, the black matrix hides, from a displayscreen side of the color filter, all outline portions of the colorlessportion which can not be considered to have substantially astraight-line shape. However, such a result is not restricted to only acomposition using the black matrix. For example, the same result isobtained also in the case of a composition such that the pixel drivingbus lines formed on the substrate opposed to the color filter have afunction of the black matrix as shielding means.

Furthermore, in the certain mode, the pixel area may be substantiallypolygon-shaped on the plan view, and the colorless portion may be formedin the vicinity of any one side of the polygon along that side. Thismeasures also have an advantage that all outline portions of thecolorless portion appearing within a pixel area can become linear shapesso as to only require a simple process while the above-mentionedadvantages result.

In more advantageous mode, there may be further provided a protectivelayer covering the coloring portion and the colorless portion. Accordingto this mode, said protective layer can provide not only protection ofthe coloring layer but also flattening of a surface of the wholecoloring layer and colorless portion.

Also in the mode, a ratio of an effective area of the colorless portionto an effective area that the optical path of the second light rayoccupies may be determined in a pixel area for each color to be made, oran effective area of the colorless portion may be determined in such amanner that a chromaticity of the first light ray obtained by a coloringeffect of the first area portion in a pixel area is substantially equalto a chromaticity of the second light ray obtained by a coloring effectof the second area portion in the pixel area for each color to be made.Accordingly, the efficacy in reducing the coloring effect by thecolorless portion can be determined rationally.

Again, in order to achieve the object mentioned above, a liquid crystaldisplay device of another aspect according to the present invention usesa color filter according to the previously mentioned aspect. In theaspect, there may be provided a transflective liquid crystal displaydevice characterized in that: the color filter is provided to onesubstrate of the liquid crystal display device; the other substrate isprovided with a pixel electrode comprising a transmissive electrode partfor making the first light ray to be transmitted therethrough and areflective electrode part for making the second light ray to bereflected therefrom; and the first area portion in the color filtercorresponds to the transmissive electrode part while the second areaportion corresponds to the reflective electrode part. Such a liquidcrystal display device can have the well-balanced color purities in eachpixel, so that a high quality of color reproduction is obtained. Asstated above, if the bus lines have the function of the black matrix andthe colorless portion is be provided, then the colorless portion shouldbe arranged in such a manner that the bus lines hide the non-linearportions of the colorless portion. As a result, it offers an advantageof reduction of the variation of the effective area as stated above.

And, again, in order to achieve the object mentioned above, amanufacturing method for a color filter of the other aspect according tothe present invention is a method of manufacturing a color filter forcoloring a first light ray having a unidirectional optical path and asecond light ray having a bidirectional optical path for each pixel,comprising: a coloring material deposition step of depositing a coloringmaterial for coloring the first and second light rays on a base layer;and a step of patterning the deposited layer of coloring material toform, for each pixel, a first area portion in which the first light rayis caused to be transmitted and a second area portion in which thesecond light ray is caused to be transmitted, the first area portion andthe second area portion respectively having structures by whichdifferent coloring effects are exerted if light rays having the sameoptical path and the same property pass through those area portions. Inthis aspect, the method may further comprise a step of forming a blackmatrix for delimiting a pixel area on the base layer before the coloringmaterial deposition step. Additionally, the method may further comprisea step of forming a protective layer on the first and second areaportions. These result in a relatively simple way for manufacturing thecolor filter whereby the aforementioned effects/advantages areaccomplished.

In order to achieve the object mentioned above, a manufacturing methodfor a liquid crystal display device of yet another aspect according tothe present invention is a manufacturing method for a liquid crystaldisplay device using the above mentioned color filter, wherein the colorfilter is provided to one substrate of the liquid crystal display deviceand the other substrate is provided with a pixel electrode comprising atransmissive electrode part for making the first light ray to betransmitted therethrough and a reflective electrode part for making thesecond light ray to be reflected therefrom, the manufacturing methodfurther comprising a step of aligning the first area portion in thecolor filter with the transmissive electrode part. In this way, theliquid crystal display device which fully performs the advantages of theabove-mentioned color filter can be surely manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a color filter used in a liquidcrystal display device according to the first embodiment of the presentinvention.

FIG. 2 is a schematic enlarged plan view of one pixel area of the colorfilter of FIG. 1.

FIG. 3 is a schematic cross sectional view of the color filter takenalong the cutting line III—III of FIG. 2 when incorporating it into aliquid crystal display panel.

FIG. 4 is a schematic plan view of a color filter used in a liquidcrystal display device according to the second embodiment of the presentinvention.

FIG. 5 is a schematic enlarged plan view of one pixel area of the colorfilter of FIG. 4.

FIG. 6 is a schematic cross sectional view of the color filter takenalong the cutting line VI—VI of FIG. 5 when incorporating it into aliquid crystal display panel.

FIG. 7 is a schematic plan view of the color filter according to thesecond embodiment for describing advantages of the second embodiment.

FIG. 8 is a schematic plan view of a color filter according to acomparison example for describing advantages of the second embodiment.

FIG. 9 is a schematic plan view of a color filter used in a liquidcrystal display device according to the third embodiment of the presentinvention.

FIG. 10 is a schematic enlarged plan view of one pixel area of the colorfilter of FIG. 9.

FIG. 11 is a schematic cross sectional view of the color filter takenalong the cutting line XI—XI of FIG. 10 when incorporating it into aliquid crystal display panel.

FIG. 12 is a schematic enlarged plan view of one pixel area in the colorfilter used for a liquid crystal display device according to the fourthembodiment of the present invention.

FIG. 13 is a schematic cross sectional view of the color filter takenalong the cutting line XIII—XIII of FIG. 12 when incorporating it into aliquid crystal display panel.

FIG. 14 is a schematic enlarged plan view of one pixel area in the colorfilter used for a liquid crystal display device according to the fifthembodiment of the present invention.

FIG. 15 is a schematic cross sectional view of the color filter takenalong the cutting line XV—XV of FIG. 14 when incorporating it into aliquid crystal display panel.

FIG. 16 is a schematic cross sectional view of a color filter accordingto a modification of the second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Now the above-mentioned aspects and other aspects according to thepresent invention will be described in more detail with reference to theaccompanying drawings.

[Embodiment 1]

FIG. 1 schematically shows in a plan view a color filter 1 used in oneembodiment of transflective type liquid crystal display device accordingto the invention.

This color filter 1 is divided into longitudinal coloring area portionseach of which extends in a vertical direction of a display screen(up-and-down direction in FIG. 1), and which have coloring matters ofthe primary colors of light, e.g. red (R), green (G) and blue (B),respectively. These longitudinal coloring area portions are cyclicallyarranged in order of R, G and B in a horizontal direction of the displayscreen. One longitudinal coloring area portion (one column) may befurther divided into portions in the vertical direction, and each of thedivisional portions corresponds to a pixel. The divisional portion willbe called a pixel portion 10 hereinafter. The boundaries of the pixelportions 10 are provided with a black matrix 1BM for, e.g. protectingthe gap between the pixel portions from leaking the light. Although thelongitudinal coloring area portions are divided in the verticaldirection in FIG. 1, the pixel portions 10 (the pixel portions 10vertically aligned) of one longitudinal coloring area portion areneither isolated materially nor physically in this embodiment.

The pixel portion 10 has: a first area portion 10 t (shown by an areaenclosed by doted lines in the Figure) which allows transmission of afirst light ray L1 having a unidirectional optical path and beingemitted from the back light system; and a second area portion 10 r thatis a part of the area 10 except for the first area portion 10 t, whichallows transmission of a second light ray L2 having a bidirectionaloptical path and being incident from a display screen to be transmittedand again incident from the opposite side after transmitted. The firstarea portion 10 t and the second area portion 10 r have such a structurethat they have different coloring effects when light rays having thesame optical path and the same property are transmitted through them, asmentioned below.

FIG. 2 schematically shows an enlarged plan view of one of the pixelportions 10, and FIG. 3 shows a III—III cross-sectional view of FIG. 2in the case where the color filter is incorporated into a liquid crystaldisplay panel 100. FIG. 2 is a plan view of a pixel portion 10 of theliquid crystal display panel 100 in the case where one views from itsfront side (i.e., from the upper side in FIG. 3). It is noted that FIG.3 shows a fundamental composition of the liquid crystal display panel,wherein the minor layers, films and construction thereof are omitted forthe purpose of making clear illustration.

The first area portion 10 t and the second area portion 10 r of thepixel area portion 10 are both formed with the same coloring material,but their structures are different respectively. The first area portion10 t corresponds to a transparent area (transmissive electrode section)8 t of a pixel electrode 80 provided on a substrate 70 opposed to thearea portion 10 t via a liquid crystal layer LC. The second area portion10 r corresponds to a reflective area (reflective electrode section) 8 rof the pixel electrode 80. It is clear from FIG. 2 that the second areaportion 10 r is provided with many through holes 1 h as colorlessportions. Accordingly, the second area portion 10 r is composed of thecolorless portions and a coloring portion other than the colorlessportions.

The through holes 1 h do not have the coloring material, so that theyallows a part L2 t of the second light ray to be transmittedtherethrough with colorlessness in the second area portion 10 r. On theother hand, the coloring portion of the second area portion 10 r is asection in which the coloring material is formed, so that it allows apart L2 c of the second light ray to be transmitted to color the part L2c in the second area portion 10 r. By contrast, the first area portion10 t is composed of a coloring layer with no colorless portion, so thatthe first light ray L1 passed through the first area portion 10 t can becolored at any position of the portion 10 t.

In a plan view, the first area portion 10 t is a rectangle whose centeris at a center of the pixel area; the second area portion 10 r is in aform that is a part except that rectangle area and surrounds the firstarea portion. Thus, this embodiment is built on premises that eachelectrode section of the pixel electrode 80 is also shaped nearly equalto shapes of these area portions 10 t, 10 r on the plan view.

As shown in FIG. 3, the pixel portion 10 is formed on substrate 20 andblack matrix 1BM in an area defined by the black matrix 1BM. The blackmatrix 1BM is provided on the transparent substrate 20 on a front sideof the liquid crystal display panel, formed inside the panel, made froma light shield material and serves as light shield means.

The through holes 1 h can be easy formed by performing a patterningprocess with a mask for forming the holes in the case of forming theabove-mentioned longitudinal coloring area portions using a coloringmaterial for each color. Because such a patterning process per se iswell-known, it will not be described anymore.

Now, effects and advantages of this embodiment are described.

The first light ray L1 is emitted from a back light system (not shown),and it is colored by the coloring material of the first area portion 10t after passing through the transparent electrode portion 8 t and theliquid crystal layer LC, whereupon the light ray L1 is guided to theoutside of the panel on the front side. On the other hand, the secondlight ray L2 from the front side of the panel is transmitted through thetransparent substrate 20, and is once colored or not colored at all bypassing through the coloring portion or the through holes 1 h of thesecond area portion 10 r, and then reaches the reflecting electrode part8 r through the liquid crystal layer LC. Then, the second light ray L2is reflected by the reflecting electrode part 8 r, and is guided to thesecond area 10 r after again passing through the liquid crystal layerLC. The second light ray L2 having thus returned to the second areaportion 10 r is transmitted through the coloring portion or the throughholes 1 h of the second area portion 10 r again with or without it beingcolored, and is guided to the outside of the panel on the front side.FIG. 3 illustrates the case where the second light ray L2 c passesthrough the coloring portion when it is first incident on the secondarea portion 10 r as well as when it is again incident on the secondarea portion and the case where the second light ray L2 t passes throughthe through holes 1 h when it is first incident on the second areaportion 10 r as well as when it is again incident on the second areaportion. In these cases, the second light ray L2 c is fully subjected tothe coloring effect, but the second light ray L2 t is not subjected toit at all. However, in actual fact, there would be the cases where thesecond light ray L2 is colored or uncolored in only one of a going pathand a returning path of the second light ray L2.

Since the through holes 1 h do not color the incident light rays asmentioned above, the coloring effect for the second light ray L2entering the second area portion 10 r can be made to be different fromthat for the first light ray L1 in the first area portion 10 t, so thatthe coloring effect for the light L2 can be desirably decreased. Thatis, the first area portion 10 t and the second area portion 10 r havesuch structures that the portions 10 t and 10 r present desirablydifferent coloring effects when the light rays having the same opticalpath and the same property are transmitted through the portions.According to this structure, there are advantages as follows.

Since the first area portion 10 t colors the transmitted light ray L1having a unidirectional optical path from the back-light system, thecoloring effect is exerted only once. By contrast, the second areaportion 10 r colors the reflected light ray L2 having a bidirectionaloptical path, so that it has two chances to exert the coloring effect.Therefore, thinking about light rays of substantially equal property(including an intensity, a wavelength characteristic, etc.), thereflected light L2 would be subjected to (sensuously) almost twicedegree of coloring effect as much as in the transmitted light L1.Thereby, the color purity reproduced for the reflected light ray L2 andthe color purity reproduced for the transmitted light ray L1 may bedifferent within a pixel, and as a result the quality of the colorreproduction would be deteriorated in a whole of the display area.However, in this embodiment, in order to prevent the deviation of thecoloring effect to the reflected light, a structure of a coloringsection for the reflected light is made to be different from a structureof a coloring section for the transmitted light by providing only thesecond area portion 10 t with a plurality of through holes 1 h ascolorless portions. Thus, the coloring effect area for the reflectedlight ray L2 can be reduced, and the area through which the reflectedlight ray L2 passes can be partly colorless. Accordingly the coloringeffect for the reflected light is reduced within a pixel so as to bringthe coloring effects for the transmitted light L1 and the reflectedlight L2 into balance. It is noted that a term “coloring effect” statedherein means an efficacy representing the degree of coloring such ascolor purity, chromaticity, brightness or the like that is obtainedunder predetermined conditions including intensity, wavelengthcharacteristic, and incident area and the like of the incident light.

As a result, the balanced coloring purities of the transmitted light rayL1 and the reflected light ray L2 are obtained within a pixel, withtotal considering, while contributing to improving the displayed colorsacross the whole display area.

In the embodiment as stated above, in order to make a difference of thecoloring effects between the first area portion 10 t and the second areaportion 10 r, the multiple through holes 1 h are dispersedly arranged inthe second area portion 10 r like a grid pattern. Alternatively, suchthrough holes can have other arrangements such as a random arrangementby design, and the number thereof and area sizes can be determined asappropriate.

As stated above, the colorless portions 1 h are for reducing thecoloring effect of the reflected light L2. Next its more concreteexamples will be described regarding their area size and the like.

Now, assuming that S is an effective area of a pixel in question, St isan effective area of the first area portion 10 t, Sr is an effectivearea (an area size of the reflecting electrode part 8 r or an area onwhich all the reflected light L2 is incident) of the second area portion10 r, Sn is a total effective area of the colorless portions 1 h, therespective areas being for one pixel. A spectral reflectance R in thereflection mode under a condition of a predetermined optical modulationof the liquid crystal layer LC may be expressed as follows.R={L2t·Sn/Sr+L2c·(Sr−Sn)/Sr}·Sr/S   (1)On the other hand, a spectral transmittance T in the transmission modeunder the same condition may be expressed as follows.T=L1·St/S   (2)In the above-mentioned equations, L1, L2 t and L2 c mean ratios of anintensity of light ray inputted into the liquid crystal display panel toits original intensity.

R is calculated for each of R, G and B based on the above expression,where L2 c and L2 t are derived from substantially natural light (orlight from the front light), and the calculated result leads to achromaticity that would be yielded in the corresponding coloring layerportion. T is calculated for each one based on the above expression,where L1 is derived from the used back-light, and the calculated resultleads to a chromaticity that would be yielded in the correspondingcoloring layer portion. The value of Sn may be determined such thatthese chromaticities are equal to each other for each of the colors. Inaccordance with such a concept, a ratio (Sn/Sr) of Sn to Sr can beobtained for each color of R, G and B. The respective examples of theratios in percentage are as follows, and the well results have beenobtained by using these values.

The pixel of R: from 5 to 15%

The pixel of G: from 15 to 30%

The pixel of B: from 3 to 8%

[Embodiment 2]

Now another embodiment according to the present invention will bedescribed.

FIG. 4 schematically shows a plan view of the color filter 4 used for atransflective type liquid crystal display device according to thisembodiment.

In this color filter 4, the arrangement forms of the pixel portion 40that is the divisional section of the color filter 4 and the structureof the black matrix 4BM used are basically the same as the correspondingconstitutional elements of the color filter 1 stated above. Likewise,there are sections 40 t and 40 r corresponding to the first area portion10 t and the second area portion 10 r respectively.

In this embodiment, however, instead of that through holes 1 h, thecolorless portion 4H is provided, which has an effective area that isdetermined based on the calculation stated above or other experiences.In other words, the second area portion 40 r is a part of the pixelportion 40 except the first area portion 40 t, and is composed of asingle colorless portion 4H and a coloring portion other than theportion 4H. Put another way, the pixel portion 40 is composed of acoloring material layer 4C (see FIG. 5) and the colorless portion 4H. Inthis embodiment, the colorless portion 4H is located at the lower-leftcorner of the rectangular pixel area, and shows an isosceles triangle ofwhich a right-angle is assigned to the corner.

FIG. 5 schematically shows an enlarged plan view of one pixel portion40. FIG. 6 shows a cross sectional view of FIG. 5 along the cutting lineVI—VI in case of incorporating this color filter into a liquid crystaldisplay panel 100′. FIG. 5 also shows a plan view from the front side(the upper side in FIG. 6) of the liquid crystal display panel 100′ inFIG. 6. It is noted that FIG. 6 basically shows the liquid crystalpanel, wherein the minor layers, films, and construction thereof areomitted for the purpose of making clear illustration.

A coloring portion 4C of the pixel portion 40 comprises: the first areaportion 40 t for the first light ray L1; and a part of the second areaportion 40 r except the colorless portion 4H for a part L2 c of thesecond light ray. As with the aforementioned first area portion 10 t,the first area portion 40 t also corresponds to the transparentelectrode section 8 t of a pixel electrode 80, and the second areaportion 40 r (including the colorless portion 4H) also corresponds to areflective electrode section 8 r of the pixel electrode 80.

The colorless portion 4H is a section through which an uncoloredreflective light ray L2 t that is a part of the second light ray, thesection being formed, in this example, in an aperture form which isdefined by the coloring portion 4C and which allows an under layer ofthe coloring portion 4C i.e. the substrate 20 as its supporting layer tobe exposed. Accordingly, any light rays passed through the colorlessportion 4H are not subjected to any coloring effects.

The first area portion 40 t located within the coloring portion 4Cshows, in this example, a rectangle whose center is at a center of thepixel area. The second area portion 40 r including the colorless portion4H is a part other than the rectangle, and is in a form of surroundingthe first area portion. Thus, this embodiment is predicated on a factthat the electrode sections of the pixel electrode portion 80 have thesimilar shapes on the plan view to these areas 40 t, 40 r, respectively.

As shown in FIG. 6, the pixel portion 40 includes: a black matrix 4BMwhich is provided on the transparent substrate 20 in the front side ofthe liquid crystal display panel 100′, and which comprises a lightshield material formed on the inside of the panel; the coloring layer 4Cconsisting of e.g. a synthetic resin having a coloring ingredient, whichis formed on the substrate 20 and the black matrix 4BM in an areadelimited with the black matrix 4BM; and a colorless portion 4Hconsisting of an aperture (blank) whose profile or outline is defined bythe coloring layer 4C.

As shown in FIG. 5, the coloring portion 4C is patterned in a shapewithout the triangle part of the colorless portion 4H in the rectangularpixel portion 40.

In this embodiment, the coloring material part corresponding to thecolorless portion 4H is removed to form an aperture (or window) throughwhich the transparent substrate 20 is peeped.

The light ray L1 from a back light system (not shown) is colored by thecoloring material of the first area portion 40 t after passing throughthe transparent electrode portion 8 t and the liquid crystal layer LC,and is guided to the outside of the panel on the front side. On the onehand, one part L2 c of the external light ray from the front side of thepanel is once colored by the coloring material of the coloring portion4C of the second area portion 40 r after passing through the transparentsubstrate 20 and the coloring portion 4C, and reaches the reflectingelectrode part 8 r through the liquid crystal layer LC. And, the lightray L2 c is reflected by the reflective electrode part 8 r and returnedto the part of the coloring portion 4C of the second portion 40 r againthrough the liquid crystal layer LC and is once again colored by thecoloring portion, and then passes through the transparent substrate 20to be guided to the outside of the panel on the front side. On the otherhand, another part L2 t of the external light ray from the front side ofthe panel, entering the colorless portion 4H, is not colored by thecoloring material of the color filter after passing through thetransparent substrate 20, and reaches the reflecting electrode part 8 rthrough the liquid crystal layer LC. And, the light ray L2 t isreflected by the reflecting electrode part 8 r and returned to thecolorless portion 4H again through the liquid crystal layer LC. Andalso, the light ray L2 t is not colored by the colorless portion 4H, andis guided to the outside of the panel on the front side through thetransparent substrate 20.

As stated above, the colorless portion 4H does not color the incidentlight ray, so that it can reduce the coloring effect for the ambientlight entering to the pixel area. Accordingly, advantages can beobtained as is in the first embodiment.

It is noted that in this composition the reflected light to be coloredby nature is made to be colorless by a single independent area, so thatspotted areas are made in microscopic observation, but thus localizedcolorless light may be neglected for displaying images in macroscopicobservation in which one views an entire display screen.

And, it is noted that the action of the colorless portion 4H, resultingin the reducing the coloring effect for the reflected light may beadjusted e.g. by setting the area size or the like based on the sameconception to the first embodiment.

Furthermore, the embodiment acquires peculiar advantages by forming thecolorless portion 4H in a triangle shape as shown in FIG. 5.

FIG. 7 shows an enlarged view of the more real colorless portion 4H, andFIG. 8 shows a comparative sample therewith given for explaining thepeculiar advantages.

In order to form the colorless portion 4H, the coloring portion 4C isformed in the shape (a kind of the saw teeth shape) shown in FIG. 5, bymeans of a patterning process wherein etching-removing is partiallyperformed in much the same fashion as a patterning process using acommon stripe-formed mask corresponding to the longitudinal coloringarea portions. However, the coloring portion 4C actually obtainedbecomes like as shown in FIG. 7 in microscopic observation. That is, thecorners of the outline of the coloring portion 4C in the plan view arenot sharp ones shown in FIG. 5 but blunt ones like as shown in FIG. 7.In other words, each corner of the coloring portion 4C becomes rounder.By contrast, the straight-line portions of the outline of the coloringportion 4C in the plan view are easy formed in a straight line shapewith relatively great precision almost as expected.

In this embodiment, because of forming the colorless portion 4H to sucha triangle shape that it is obtained by trimming one corner of therectangular pixel portion 40, rounder portions of the coloring portion4C can be limited to only boundaries of the pixel such as the left sideand the lower side in FIG. 7, so that all these rounder portions can behidden by the black matrix 4BM. By virtue of the combination with theblack matrix, it is possible to accurately form the colorless portion 4Hhaving desired shape and area size. Furthermore, there is also an aspectthat such triangle shaped colorless portions 4H have little variationsand are easy formed in relatively equal areas.

By constant, in the case of forming the colorless portion (4H) in arectangle, the rounder portion 4Co would remain in the coloring portion(4C) even if it were combined with the black matrix (4BM), as shown inFIG. 8. Such a rounder portion is difficult to be predicted with regardto its degree of roundness. In addition the rounder portions would havea wide range of variations, so that they should be exceedinglydisadvantageous in respect that the colorless portions are formed withdesired shape and area size.

In this embodiment, a planar shape of the colorless portion 4H is anisosceles triangle to thereby further offer a more advantageous examplethan a scalene triangle. That is, as long as the colorless portion 4H isthe isosceles triangle, even if the mask to be used for patterning ofthe coloring portion 4C deviates in upward and downward directionsand/or leftward and rightward directions, then the colorless portion 4Hshows the geometrically similar isosceles triangle and changes its areawith an across-the-board degree in accordance with the deviation. Byconstant, in the case of the non-isosceles triangle, the degree ofarea-changing when it deviates in the upward and downward directionsdiffers from that when it deviates in the leftward and rightwarddirections. Upon reconsidering the matter, in the case of the isoscelestriangle such as in this embodiment, the area-changing of the colorlessportion 4H responsive to the deviation of the mask is easy in control,so that an advantage can be expected in that a high accuracy on formingthe mask or the like is not required.

Furthermore, in the case of forming colorless portions having the samearea size, by making the areas triangle-shaped, it is able to easy makea length of the edge of the coloring portion 4C along which the outlineof the colorless portion 4H is formed to be shorter than in the case ofthe other shaped areas. Therefore, the step portion between the coloringportion 4C and the colorless portions 4H can be made smaller toadvantageously contribute to flattening a surface of the color filter.

[Embodiment 3]

In the second embodiment, the description has been given about theexample in the case of forming the colorless portions 4H in a triangleshape, but the peculiar advantages can also be obtained by forming themin other shapes.

FIG. 9 schematically and in general shows in a plan view a color filter4′ of this embodiment. FIG. 10 shows a view partly enlarged therefrom,and FIG. 11 shows a cross-sectional view of FIG. 10 along the cuttingline XI—XI.

As is evident from FIG. 9, the colorless portion 4H′ is formed in arectangle that extends along the entire one side of the rectangularpixel portion 40′ in a shape of straight line near the side. Thiscolorless portion 4H′ of this example may be a groove-shaped portionextending in a vertical direction of the display screen as seen fromFIG. 11.

Also by forming such a colorless portion 4H′, all the edges of thecoloring portion 4C′ appearing in a pixel area are straight line shaped,so that the variations are in a narrow range and the colorless portion4H′ is easy to be accurately formed with the desired area. Besides, thisembodiment is realized by just narrowing the width of the coloringportion 4C′. Therefore, the patterning process in the embodiment may bea very similar to a patterning process used in the prior art for stripeshaped coloring portions, so that an advantage concerning a managementof manufacturing processes is expected.

[Embodiment 4]

In order to provide the different coloring effects to the first areaportion and the second area portion, yet another constitution as shownin FIGS. 12 and 13 is available.

FIG. 12 schematically shows an enlarged plan view of a pixel portion 50of the color filter according to the fourth embodiment and FIG. 13 showsa sectional view of FIG. 12 along the cutting line XIII—XIII in the caseof installing this color filter onto a liquid crystal display panel100′″.

In this embodiment, the first area portion 50 t and the second areaportion 50 r have such structures that their densities of coloringelement formed are different from each other. To this end, each of thefirst area portion 50 t and the second area portion 50 r has at least asurface layer portion formed in a plurality of coloring elementconstruction units, in this example, based on a projecting body elementof coloring material used as a construction unit pattern (bump, morespecifically a generally hemispherical protuberance) and bumps 5 b ofthe first area portion 50 t are formed with a higher density than bumps5 b of the second area portion 50 r.

According to this embodiment, it is possible to make a difference inconstruction between the first area portion and the second area portionfor achieving the intended object, while it is possible to easy make adifference of the effective surface area or volume of coloring elementsto work on the coloring effects for the incident light rays between thefirst area portion 50 t and the second area portion 50 r by a patterningprocess.

[Embodiment 5]

Furthermore, a configuration as shown in FIGS. 14 and 15 is alsoimplemented.

FIG. 14 schematically shows an enlarged plan view of a pixel portion 60of a color filter according to the fifth embodiment, and FIG. 15 shows asectional view of FIG. 14 along the cutting line XV—XV in the case ofinstalling this color filter in a liquid crystal display panel 100″″.

This embodiment also proposes that the first area portion 60 t and thesecond area portion 60 r have such structures that their densities ofcoloring element formed are different from each other. To this end, eachof the first area portion 60 t and the second area portion 60 r has atleast a surface layer portion formed in a plurality of coloring elementconstruction units, in this example, based on a depression body elementof coloring material used as a construction unit pattern (dimple, morespecifically a generally hemispherical hollow) and a dimples 6 d of thesecond area portion 60 r are formed, here, with a higher density thandimples 6 d of the first area portion 60 t.

According to this embodiment it is possible to make a difference inconstruction between the first area portion and the second area portionfor achieving the intended object, while it is possible to easy make adifference of the effective surface area or volume of coloring elementsto work on the coloring effects for the incident light rays between thefirst area portion 60 t and the second area portion 60 r by a patterningprocess.

It is noted that the first area portion and the second area portion areformed based on the pattern of bumps or dimples, so that their surfacesare roughened, whereby the incident light rays can be diffused. Thesediffused light rays improve a visible angle characteristic on thedisplay screen to contribute to further improvement of visibility, andin particular, it is effective on the light ray L2 in the reflectionmode.

Furthermore, there may be an embodiment based on combination of featuresof the fourth and fifth embodiments. That is, it may be intended toobtain the desired difference in coloring effect by combining the firstarea portion 50 t (high density formational structure of coloringelement) in the fourth embodiment with the second area portion 60 r (lowdensity formational structure of the same) in the fifth embodiment, andalternatively to obtain the desired difference in coloring effect bycombining the first area portion 60 t (high density formationalstructure of the same) in the fifth embodiment and the second areaportion 50 r (low density formational structure of the same) in thefourth embodiment.

In the embodiments stated above, since the pixel portion is providedwith the holes 1 h, colorless portion 4H, 4H′ or has form of projectionsand depressions of the bumps 5 b and the dimples 6 d, some steppedportion is formed in the coloring portion to degrade the surfaceflatness of the whole color filter. Such a step would be oftendisadvantageous with regard to aspect of the optical characteristics orthe like.

In view of this point an example that improves the second embodiment isshown in FIG. 16 as the representative. In this embodiment, a protectivelayer 9 as an over coat layer consisting of a synthetic resin isoverlaid on the coloring portion 4C and the colorless portion 4H forprotecting the coloring portion 4C, and the aperture portion of thecolorless portion 4H is buried to flatten the surface of the colorfilter. This protective layer consists of the optically transparentmaterial, so that it is able to exert no influence upon the coloringeffect of the color filter.

By virtue of this flattening of the surface of the color filter by theprotective layer 9, faces on which light is incident in the surface aremade uniform. This can prevent e.g. the unexpected light leakage causedby asperities associated with openings of the colorless portion 4H tosignificantly contribute to improvement in the optical characteristics.

Furthermore, even if other film such as an orientation film (not shown)or the like is provided on the color filter, the coloring portion 4C isavoided from directly being in contact with the other film, so thatthere is an advantage in that contamination of the liquid crystal layeris prevented. In addition, by virtue of the flattening of the surface ofthe color filter, it is convenient to avoid irregularity of theorientation in an orientation layer or the liquid crystal layer LCarranged on or above.

Also in the other embodiment, providing the protective layer 9 in muchthe same manner leads to the same advantages. However, in the case of aspecific composition such as the Embodiments 1, 4 and 5, the degree ofevenness is small, so that the protective layer can be thinner than oneapplied to the Embodiment 2 when the same flatness of filter isintended. That is, the specific composition itself has high flatness ofthe surface of the color filter, so that it can be said that littleinfluence caused by the uneven shape is exerted upon the other layers.

By the way, in the embodiments as stated above, it has been mentionedthat the pixel portion of the color filter is rectangular, and it hasbeen mentioned about the examples of including the rectangle-shapedfirst area portion for transmission and the second area portion forreflection, having a shape of surrounding the first area portion.However, the present invention is not necessarily limited to suchexamples. Such a pixel portion (pixel area) may be in other type ofshape than a rectangle, such as a polygon having 5 or more sides. Thefirst area portion may be in other type of shape than a rectanglelikewise, and/or may be divided into plural sections.

Fundamentally, the area for transmission and the area for reflection inthe color filter correspond to the areas (in the embodiments givenherein, respective areas of the transmissive portion and the reflectiveportion formed in the pixel electrode) assigned for the first light(ray) and the second light (ray) handled in the display device inquestion, respectively. The areas for transmission and reflection arethe same as the assigned areas in shape, layout and the number.Therefore, instead of the rectangle shaped first area portion and thesecond area portion surrounding the first area portion in theabove-mentioned embodiments, the first area portion may be circle-shapedin a plan view, almost rectangle-shaped but rounding-shaped (includingan ellipse), or polygon-shaped based on 5 or more surrounding sides.

It is noted that other various modifications can be realized in thepresent invention. For example, the pixel portions may be in the othershape than a grid pattern as shown FIGS. 1. 4 and 9. Although there hasbeen mentioned the example in which the color filter is directly formedon the substrate 20 in the above embodiments, some under layer may beinserted between the substrate 20 and the color filter. Namely, thepresent invention is directed to a color filter that may be supported byany base layer including such an underlayer and the substrate.

Instead of the protective layer 9 being perfectly transparent withoutany color, it may be one having some coloring property for a certaindesired purpose. In the above embodiments, there is stated a colorfilter based on R, G, B primary colors for making full color pictures,but the present invention is applicable to a monochrome color filterdedicated to monochrome pictures.

The preferred embodiments described herein are therefore illustrativeand not restrictive, the scope of the present invention being indicatedby the appended claims, and all variations which come within the meaningof the claims are intended to be embraced therein.

1. A color filter for coloring a first light ray having a unidirectionaloptical path and a second light ray having a bidirectional optical pathfor each pixel, the color filter including: a first area portion inwhich the first light ray is caused to be transmitted and a second areaportion in which the second light ray is caused to be transmitted, foreach pixel, the first area portion and the second area portionrespectively having structures by which different coloring effects areexerted if light rays having the same optical path and the same propertypass through them, wherein each of the first area portion and the secondarea portion has a coloring element surface that is patterned based on aplurality of unit patterns, and the first area portion and the secondarea portion have different densities of the unit patterns per surfacearea of the pixel.
 2. The color filter of claim 1, wherein the firstarea portion and the second area portion have such a difference indensities of the unit patterns that a coloring effect performed for thefirst light ray within a pixel by the first area portion issubstantially equal to a coloring effect performed for the second lightray within a pixel by the second area portion under predeterminedconditions.
 3. The color filter of claim 1, wherein the second areaportion includes a coloring portion that colors the second light ray andat least one colorless portion that transmits the second light raysubstantially with colorlessness.
 4. The color filter of claim 1,wherein the unit pattern is projection-shaped, and the unit patterns ofthe first area portion has a higher density than the unit patterns ofthe second area portion.
 5. The color filter of claim 1, wherein theunit pattern is depression-shaped, and the unit patterns of the firstarea portion have a lower density than the unit patterns of the secondarea portion.
 6. The color filter of claim 1, wherein the unit patternhas a shape with a function of diffusing incident light.
 7. The colorfilter of claim 1, wherein the first and second area portions are formedfrom the same coloring material.
 8. The color filter of claim 1, whereinthe color filter includes a protective film covering the first andsecond area portions.
 9. The color filter as defined in claim 3, whereina plurality of the colorless portions are dispersedly located over thesecond area portion.
 10. The color filter of claim 3, wherein the pixelarea has substantially a polygon shape on a plan view, and the colorlessportion is located in the vicinity of a corner of the polygon in a pixelarea.
 11. The color filter of claim 3, wherein the pixel area hassubstantially a polygon shape on a plan view, and the colorless portionhas a shape of substantially a triangle including a corner of thepolygon and having an oblique side opposed to that corner in a pixelarea.
 12. The color filter of claim 11, wherein the colorless portion isisosceles-triangle-shaped on the plan view.
 13. The color filter ofclaim 3, including a shield disposed about a boundary of the pixel area.14. The color filter of claim 11, wherein the shield is configured tohide, from a display screen side of the color filter, peripheralportions of the colorless portion that do not have a substantiallystraight-line shape.
 15. The color filter of claim 3, wherein the pixelarea is substantially polygon-shaped on a plan view, and the colorlessportion is formed in the vicinity of any one side of the polygon alongthat side.
 16. The color filter of claim 4, wherein a ratio of aneffective area of the colorless portion to an effective area that theoptical path of the second light ray occupies is determined in a pixelarea for each color to be made.
 17. The color filter of claim 3, whereinan effective area of the colorless portion is determined in such amanner that a chromaticity of the first light ray obtained by a coloringeffect of the first area portion in a pixel area is substantially equalto a chromaticity of the second light ray obtained by a coloring effectof the second area portion in the pixel area for each color to be made.18. A liquid crystal display device using the color filter of claim 1.19. The liquid crystal display device of claim 18, wherein: the colorfilter is provided to one substrate of the liquid crystal displaydevice; an other substrate is provided with a pixel electrode thatincludes a transmissive electrode part for making the first light ray tobe transmitted therethrough and a reflective electrode part for makingthe second light ray to be reflected therefrom; and the first areaportion in the color filter corresponds to the transmissive electrodepart while the second area portion corresponds to the reflectiveelectrode part.
 20. A manufacturing method for a liquid crystal displaydevice using the color filter of claim 1, wherein the color filter isprovided to one substrate of the liquid crystal display device and another substrate is provided with a pixel electrode that includes atransmissive electrode part for making the first light ray to betransmitted therethrough and a reflective electrode part for making thesecond light ray to be reflected therefrom, wherein the manufacturingmethod includes aligning the first area portion in the color filter withthe transmissive electrode part and aligning the second area portionwith the reflective electrode part.
 21. A color filter for coloring afirst light ray having a unidirectional optical path and a second lightray having a bidirectional optical path for each pixel, the color filterincluding: a first area portion in which the first light ray is causedto be transmitted, and a second area portion in which the second lightray is caused to be transmitted, for each pixel, the first area portionand the second area portion respectively having structures by whichdifferent coloring effects are exerted if light rays having the sameoptical path and the same property pass through them, wherein each ofthe first area portion and the second area portion is formed based on aplurality of coloring element construction units having a non-uniformprofile, and in that the coloring element construction units of thefirst area portion have a higher density than those of the second areaportion.
 22. A color filter for coloring a first light ray having aunidirectional optical path and a second light ray having abidirectional optical path for each pixel, the color filter including: afirst area portion in which the first light ray is caused to betransmitted, and a second area portion in which the second light ray iscaused to be transmitted, for each pixel, the first area portion and thesecond area portion respectively having structures by which differentcoloring effects are exerted if light rays having the same optical pathand the same property pass through them, wherein the first area portionand the second area portion have coloring element surfaces that arepatterned based on a plurality of first unit patterns and on a pluralityof second unit patterns, respectively, and in that the unit patterndensities of the first area portion and the second area portion aredetermined so that the first and second area portions have suchstructures that coloring element forming densities of the first andsecond area portions are different from each other.
 23. The color filterof claim 22, wherein the first unit pattern has one of projection shapeand depression shape, and the second unit pattern has an other ofprojection shape and depression shape.
 24. A method of manufacturing acolor filter for coloring a first light ray having a unidirectionaloptical path and a second light ray having a bidirectional optical pathfor each pixel, comprising: depositing a coloring material for coloringthe first and second light rays on a base layer; and patterning thedeposited layer of coloring material to form, for each pixel, a firstarea portion in which the first light ray is caused to be transmittedand a second area portion in which the second light ray is caused to betransmitted, the first area portion and the second area portionrespectively having structures by which different coloring effects areexerted if light rays having the same optical path and the same propertypass through those area portions, each of the structures of the firstarea portion and the second area portion having a non-uniform profile.25. The method of claim 24, including forming a black matrix fordelimiting a pixel area on the base layer before the coloring materialdeposition step.
 26. The method of claim 24, wherein the method includesforming a protective layer at least in part on the first and second areaportions.